1. Field of the Invention
Carpule syringe with equipment for detachably and positively holding the hub of a hypodermic needle.
2. Description of the Prior Art
Carpule syringes are a relatively new entry into the medical field. They have come to be widely used and accepted, particularly where syringes are to be loaded and used repetitively. Syringes of this nature facilitate repeated loading. They lend themselves well to rapid, simple and easy insertion of fresh doses of medicament and discharge of exhausted containers. A carpule syringe, also known as a cartridge syringe, is characterized by the absence, as in a standard syringe, of a fixed barrel in which a piston reciprocates. Instead, a carpule syringe includes a frame with a large side opening designed to transversely receive a pre-filled, i.e. loaded, cartridge, the ends of which are closed and hermetically sealed. After insertion in the frame, the cartridge is locked in place. The forward end of the cartridge is closed by a plug that includes a thin, easily penetratable, self-sealing membrane. The rear end of the cartridge is closed by a plug which is capable of slidable movement within the cartridge. The frame is provided with a reciprocatable shaft arranged to be engaged with the plug under the control of an operator so that when the shaft is pushed forwardly in the frame, it will push the plug forwardly and thereby apply pressure to the liquid medicament within the cartridge so as to dispense the same through a hypodermic needle. A special hypodermic needle is used which is located at the front of the frame. This needle has a hub between its ends which is screwed into the front of the frame. The needle includes a rearwardly extended pointed segment which pierces the thin membrane at the front of the cartridge when the cartridge is inserted in the frame so as to couple the needle to the liquid medicament. Such arrangement enables cartridge after cartridge to be inserted into the frame where it is immediately ready for use, to be used until exhausted and to be replaced with a fresh cartridge time after time, quickly and expeditiously.
Carpules, of course, like all other medical equipment, have their problems. A major problem is that the connection between the hub of the syringe and the front of the frame is a threaded one. The hub has a male thread and the frame has a female thread. One of these threads wears out after extended use, usually the thread on the frame. It seems a matter of fate that when the failure occurs it is at an inopportune time, namely, when the syringe is embedded in a patient's flesh. When this occurs, after injection, and the doctor or clinician tries to pull out the needle, all that he will succeed in doing is to pull the frame away, leaving the needle with the attached hub embedded in the patient's flesh. The needle now must be delicately removed from the patient, usually with considerable discomfort and anxiety to the patient. This happens with far too great frequency. It is the purpose of the present invention to avoid this particular difficulty.
One proposal has been made to solve the problem above mentioned. This is embodied in Lingley U.S. Pat. No. 2,806,473 in which a carpule type syringe uses a double-ended syringe needle the inner end of which is disposed to pierce the seal at the outer end of the cartridge and in which a clip on the frame presses a hub of the needle against the frame of the syringe. The problem is not the same as the problem with which applicant is concerned, inasmuch as applicant's problem is unique to a carpule type syringe in which the needle has a hub screwed into the frame of the syringe, so that the needle is used repeatedly and there is an erosion of the joint between the hub and the syringe frame, i.e. of the mechanical coupling between the hub and the frame. The same distinction is true of Macgregor U.S. Pat. No. 2,695,613. Kauffman U.S. Pat. No. 2,047,512 and Burnside U.S. Pat. No. 2,604,890 represent other approaches to the same problem which are not relevent because they are not designed to function with commercially available carpule syringes having a female threaded front end. Haines U.S. Pat. No. 1,591,761 discloses a hypodermic syringe which employs a clamp to lock in place a needle hub the frusto conical socket of which is seated on a frusto conical tip at the discharge end of the syringe barrel; however the syringe is not a carpule type syringe.